Drill



July 27, 1943. A. J. NORDBERG 2,325,535

INVENTOR.

July 27,1943 A. J. NORDBERG ed Oct. 28,V 1941 2 Sheets-Sheet 2 PatentedJuly 27, 1943 i,ll\ll'l'EDY STATES PATENT OFFICE f V 1 2,325,535 A DRILLAlbert I. Nordberg, Detroit', Mich. Application (lct'ober 28, 1941,Serial No. 416,851v

7.Y Claims;

This invention relates to the manufacture -of rifle barrels and has forits principal objects to provide a new and improved construction of adrill especiallytadapted for such work by means of which the rate ofrproduction is greatly increased and the cost of manufacture decreased.The drilling ora rie barreL- and particularly barrels for militaryrifles, has, with the production nfiethods heretofore employed,-been avery diiiicult, time consuming operation that` was capable of beingperformed only by-the most highly skilled mechanic.' The barrels ofmilitary rifles are quite long, usually from .45 to 90 inches in length,and have heretofore been finished by the use of a special drill whichmust of necessity be longer than the rifle barrel. As the'bore of thebarrel must be perfectly straight and smooth, great care must belemployed to prevent the tool from scoring the gun b-arrel as the resultof gouging or as a result of the accumulation o-ipchips and consequentseizing of the drill in thebarrel'and like- Wise. great care mustbeexercised to prevent the drill from drifting sidewise during thedrilling operation which'would Vresult in the production of a borethatisnot perfectly straight. Allowable tolerances being ofthe nature'offractions of one thousandths of an inch; the most meticulous accuracy isrequired.

It has beenrfound that because of the great length of the; barrelrelative to the diameter thereof, barrels couldnot be drilled or boredby the use of an ordinary twist drill or by the use of a boring bar, andit has been the practice for many years to employ a special singleiluted drill in which the ute provided for chip clearance extendsparallel withV the axis of the drill. Such drills as heretofore usedhave almost universally been mounted horizontally in special machineswhich have required the services of highly skilled mechanics for theiroperation anddue tofthe great length of the drill and its comparativelysmall diameter, such drills as heretofore used have had but veryslightresistance to torque. Consequently thel operators of the gun barreldrilling machines have had to develop an almost uncanny ability toperceive almostl instantaneously when, in drilling a gun barrehthetorque thrown upon the drill threatened to become great enough, eitheras a result of chip accumulation or from any other cause, to throw thecutting edge of the drill out of proper alignment or to place strainenough upno the drill as to cause it to break.

a piece of steel tubing, one sidewall of which has been pressed orrolled tokprovideuthe chip clearance flute and to the end of whichtubing a piece of tool steel has been brazed or Welded toform thecutting end or bit of the tool. Due tothe manner in which the shankportion of the cutting drill has beenlfabricatedtby pressing in o neside wall of the tube to` form a chip clearance flute and also toprovide an oil passage 'extending longitudinally through the shank, avery definite limitation has of necessity been imposed. upon thethickness of the wall of the tube employed.

Among the'principal objects of the present in-V vention are to` providea new and improveddrill for the fabrication of rifle barrelsin which theshank portion of the drill is constructed of la tube having amuch'thicke'rrtube wall than heretofore employed so that the drill canwithstand Aheavier torque strains and to obtain the desired shape ofchip clearance iiutewhile insuring an outerconsuflicient volume, all ofthe above described resuits being obtained as the resultV of a novelmethod of fabricating the drill shank as will -pr'ersf ently be morefully described.

Another object is to provide a drill of this character ,withA a cuttingbit portion formedof the well known tungsten carbide type` of materialsuch as sold under'various trade names as for example Carboloy. f l

A further object is to provide anew and im-4 proved construction of the4means for combining thel improved type of drill shank with a'phigh speedcutting bit toform4 a unitary structure and to unite the cutting bitportion with the tool shank in such a Way that a smooth continuous outersurface will be formed on the drill and further to provide the cuttingbit portion with lands and relieved portionsiadiacent thereto that vwilleiiectu'ally cooperate with the drilled or ,bored portion of the hole toprevent any lateral drifting of the drill Vduring the boring operationWhile Drills, as heretofore employed for this purpose, W

have consisted of a main shank portion formed of at the sainetime'insuring proper clearances lfor effective cutting.

The above and other objects of the invention Wlli appear moreY fullyfromthe followinglmore detailed description and by reference to theaccompanying 'drawings forming a part hereof, wherein: A A t Fig. 1 is4.aside elevationrshowing the improved manner inrwhich the drill of thepresent invention is employed in machining the bore of a 'riile barrel;

"vFiguZ is a plan view of the cutting end of the drill as seen from line2 2 in Fig. l;

Fig. 3 is a longitudinal section taken along theA line 3--3 of Fig. 2and showing the component Yparts of the drill united to form a unitarystruc- .Fig. l2 is a perspective View of such shank por` tion when innished condition.

As shown in the drawings the drill bit of the present inventioncomprises a main shank portion 20 constructed of steel tubing in amanner presently to be described more fully, an yintermediate tool bitholder portion 22 and a" cutting l bit or tip 23. The shank portion 2Bof the drill,

'as' clearlys'howrlv in Fig. l2, is provided along substantially; itsentire-length" with aflongitul din'ally fextending u'te V2li to'Vprovide for 'chip clearance. Afterf the r:shank -prtiori` has beenfabricated thetool bit holder 22 which may" be constructed of highYcarbon steel, is secured to the end of the shank portion 2l? anordinarybrazing; as indicated' by'the reference character25.\-"1`he^intermediate bit holder" portion 2v2 is preferably-made ofv apiece o'f solid barfstocl which at`its-inner end yissquared oir forready attachment tol the'tool Vshank 2B while the other endfthereof Yismachined out to form va' recess or;V socket 26 into which Athe similarlyshaped inner end ofthe cutting bit portion'23 is adapted to be seated. Y`The cutting bit 23 is preferably constructed of; one ofthe highspeedduty compositions-*such as tungsten carbide of the' type known asfBarboloymor the like vand issecureol` to the' bit holder/portion'22 bycopperbrazingjfthe recess 23 of the holder'22 and sirnilarlyshaped innerend of the bit23 being provided Yfor the purpose of Ifroviding a greatersurface-'area `of Abrazedv `j oints toinns'ure amore:intirnateunitingofthe parts for Yithstanding `the torquek stresses placed i upon thedrill1when-`in^Servicer` llhe bit 23 and holder 22 are provided with alongitudinally'7 'extending hole" 2lL which" forr'ns a conduit' for oilunder: pressure' and which is 'in communication with l a conduitfZiif`formed `in the shankportionZ ofthe drill'.` The bit'portion'23 Yofvtheir drill has its outer end groundito provide a'spec'ial type 'of a'cutting edge 2'9fvsuc'h'as usually employed for gunbarreldrillsandformed byone side of the nnte 3o pro-Imaam the apporti@ 23, The-flute 30j is arranged' in*Y"longitudinal align-l nient with a similarflute :ie-r p'mrnjldedein the holder portion 22' and which'issirnilarlyaligned with* the similar IiuteZ formed in the shank por;nonzu oftneidrring In "ojrdertoA insure eicient cuttings action of the"tool bitV and, to insure ample lateral" support Vthereof toprevent'sidewisedrifting ofthe cut'- ting" end 'ofthe VYdrilljthetool'bit portion'ispro vided on that V4side of" the; ute'SG, "the'end ofwhich forms the cutting edgerZSL'witha'land 32 tnefwldth of whiehisofthe @merci abouti-2- of anj-inch whilethe opposite side lof the" drilladjacent the jsi'dev` edgeV 33 of "the `flute 33 'is pro. vided'with awider land 34 and that portion'of the tool bit diametrically oppositefrom the nnte 30j vis provided with eilanden a 'rneftnreelandsjs g,34fand135"are the .fulldiainete'rf'of 'the toolbit and ef th-hole to tedriuediwhiie those-poni wall of the tube employedforthese'drill,shan

Y @beigelegt new.

of the tool bit between the land 32 and 35 and 34 and 35 respectivelyare relieved as indicated at 36 and 3l to reduce the frictional contactarea between the drill and the hole drilled thereby. The bit holderYportion 22 is also provided with lands and relieved portions similar tothose provided in the cutting bit 23.

After the parts 20, 22 and 23 have been united together as indicated inFig. 3, the ash formed bythe brazing 25 is ground oil? and the parts arethenfpref-erably subjected to a plating or nitriding operation, butpreferably chrome plating, which serves'to form a continuous outerksurface along the three assembled portions and to completely cover thejoints between the respective parts formed by the brazing of the bit 23to theholder 22 and of the latter to the shank 2e, the plated coatingbeing built up to a point a 'few thousandth'sabove the desired nishedouter diameter and then being ground down to the exact dimension, theouter plated coating of the parts Vas indicatedlv by therefer'encecharacter 38 being shown in' va somewhat exaggerated formnFgA- ai Y Y In contradistinction to the methods hereto# fore employedfor'th'e boring of rifle barrels and in' which the drill was' held inhori'zoiitalposition,V I have found that much better results and ahigherrateof production can be procured by holding the drill stationaryin any suitable hold"- er vor chuck,v as indicated bythe reference character 3.9 in Fig.' l, While the rifle barrel 4S: 'to be' drilledorb'ored 'isrotated rapidly and'fed downwardly' over thedrill' asl'indicated by the arrowinFig.`1.

`In the drilling of the rifle barrels it has always beenv the 'practiceto supply oil or other suitable cutting fluid under extremely highpressurethrough the central tubular'part l28 of the drin lShank and'connecting conduit 21 under' Yvery high pressure and to rely upon thepressure of the cuttingy fluid to carry awaythe chips and wash themthrough theflute'fil to vthe"ba-cl;V edd of the driuff-By mounting `vthedrin' in a vertical positi'onand feeding the gun barreld downwardly VonVto the drill as Yindicated in'Fig. l2 the force of gravity carries the'chip's'downwardl'y alOngWth the"t fluid 'td be ejectd'jttl'e bcli endof the drill and it is not;'tlf're'refore; ne'ci essa'ry' withv adrillasdisclosed and'u'sed' in Eaccordance with-the presentinvention, ftoresort to such'-Y extremely higli'ipressures' "for the"c1t4- tingrnuidx'I' 'f f f' As hereinbeiore explained the shank portion 2l] oftheeuttin'g anus 'heretofore 'empioy'eafortn drilling'of gun 'barrelsliavefa y beerrfc'onl Structed 'of arpie'eefof, tube-st o of whichnasrbeen rolled; er pressednwdly "toi ferm me c1earancel netese;tneefeeftilefwas 'lf' the v s' Moreoveras" the flute portion' wasyforrned'veni; tireiy'b'y A 'reumgendf drawing; tneffi'w "or tri metalproduced-a very appreciable "curvature-of the rnetal'fofrthve'tubeinthose portio'sf't "'eieof immediateiyiedjaeen" the "clearanceVcute wenn resulted 1 in* a* cqirespondmg*aporecitle decrease indiameter offtliesnanl'be1-ow 'the Ede; si'red lnished iln'ensionattlfezplaoe1 twhe l`the full dimension offthe drill'y Wasrno'stneededfor a'very decidedfliniitationin the thiikness o lateral supporttpreventenfnngend Migrating;

' limi-@Cree 'the ffmlrflaiieh 'Of shank.. inw the desiredcongurationAto' providdthe chipf c af: an@ @die by bending androiiolg the me"2525,535 ness or the 'wan tute tnatcuid be used for 'drin shanksfabricated in the manner heretofore em" ployed, resulted in a finalproduct which had veryV slighty resistance tothe torque which the drillwas called upon to resist in performing its intendedcutting function.

In order to avoid the above' mentioned unde-v sirable featuresandto'providea contour ofthe drillv shank in which the shank would be ofthe desired full diameter closely adjacentto the chip clearance fluteand so that the shank can be constructed of muchiheavier tubing betterable to withstand the torque stresses; the Vdrill shank of the presentinvention" is constructedin the manner indicated Vby the" seriesof viewsFigs. 6. to l1 of the drawings.` A

In fabricating the 'shank Vportion a relatively thick walledstubeZUJ--aV as shown inV Fig, 6k is employed. This tube then has4 aVportionveof oneV side wall thereof cut away by any suitable means such;for example, as a' form milling cutter to provide the`converging sidewall portionsr or flats Eiland to reduce the tubelalong its entirelength to the `form shown in Fig.` 'l of the drawings.V

This operation, it will'jbe seen, reduces the wall El of thetubeadjacentthe flats 50 particularly at the'central point thereof lto a thicknessapproximately one-half of the original thicknessof Ythe tube walk Thetube is'next subjected to a rolling operationwhich presses the thin wallportion 5i `of the tube inwardly towards the center thereof andcauses'the flats 50 to be merged into a single flat surface 52 whichbears the relation of a chord to the original circularrcross .section ofthe tube. i

The next step in the formation of the shank is to subject' the flat wall52 Vto a further rolling operation, thereby forcing the thin' wall 5|fur-V ther towardsthe centerline ofthe tube and to` transform the flatWall 5.2 into the 're-entrant'arcuate or convex wall 53v and tobring thetube tofthe form shown in`Fig. il of,` the drawings. The tube is then'subjected'to another rolling operation which forces the thin wall 5|thereof slightly past the center of the tube and towards the oppositethicker'wall and to form a pair of fiat-s 54 forming a re-entrant angleand leaving the tube in the condition shown in Fig. l0 of the drawings.e

The next step is to subject the tube to still a further rollingoperation in which the wall 5| is pressed still farther towards theopposite side wall and to form the chip clearance flute 24 inV the shank20, this iiute having side wall portions 25J-a and 33-a which correspondwith the similar side walls 29 and 30 of the toolbit portion 23. As thetube leaves the rollers which press the wall 5| downwardly to theposition shown in Fig. 11, the tube then is subjected to the action of agroup or finishing rolls which engage the outer arcuate surface ofthetube adjacent the edges of the flute walls 29-a and 33-a, thereby toinsure that substantially the entire outer curved surfaces of the tubewill be of the required diameter and free from any protuberances; thetube in its nal condition being as shown in Fig. 1l in which theoriginal-cylindrical bore has been. converted from its circular crosssectional form into a somewhat crescent shape which forms the conduit 28by means of which cutting fluid under end of the shank by a simple buttwelding o1' brazing operation as hereinbefore described.

As'will be seen from an inspection of the cross sectional View ofFg. 11the shank 2B in its final form has the major portion of its arcuate sidewall portions 60 of a thickness substantially twice that of thethickness of theside wall portion 5| at the flute'p'ortion of the shank,the major portion of 'the torque reaction being transmitted to the shankin the direction of the arrow A in Fig. 11, is therefore, communicateddirectly to the thicker sidewall 60 with the'result that a drillprovidedwith a shank of the type shown in the drawings offers veryeffective resistance to the torque stresses. t v v' It will also be seenfrom an inspection of Fig. l1 thatthe opening formed by the crescentshaped conduit 28 Aforms but aminor portion of the cross sectional areaof the shank-the major portion thereof being formed of the solid metalof the tube walls. .Due to the greatly reduced area to .the conduit 28over devices of the type heretofore vAnother feature'ofV greatimportance in a tool;

shank constructed in accordance with the present invention is that dueto the method Of fabricatingthe shank the outer curved surface thereofis maintained at substantially the full diameter up to a point veryclose to the side walls 29-1-a and 33-a of the flute portion 24 andconsequently the shank is of the full dimension of the hole to be'drilled for very much more than the semi-circumference of its circularcross section. This insures that the shank will be in lateral contactingengagement with the bore of the hole to be Vdrilled'closely adjacent tothe flute portions thereof at which point-*the need for lateral supportis greatest. 1

In using the drill of the present invention it is, ashereinbeforepointed out, preferably supported in a vertical position as indicated inFig. l of the drawings. The bit portion of the drill hav- 'ing beenformed as hereinbefore described and as illustrated in Figs. 2 and 3 ofthedrawings and the drill preferably being provided with a high speedduty type of cutting bit or tip, the rifle barrel 40 may be rotated at aspeed of rotation many times greater than that employed with the drillsas hereinbefore constructed, and consequently it is not necessary inorder to get remarkable increased production, to use a heavy feed thatwould place heavy torque stresses upon the drill. As the chips are cutaway by the cutting edges of the tool from the gun barrel, such chipswill tend to drop by the force of gravity to the fluted portion thereofand prevent any undesirable accumulation of chips either adjacent thecutting edge of the drill or along the shank portions thereof. However,as an added precaution against chip accumulation, oil under pressure issupplied from a suitable source of fluid pressure through the crescentshaped conduit 28 of the shank 20 to pass therefrom to the hole orconduit 2l provided in the bit holder 22 and bit 23 to be deliveredimmediately adjacent the cutting edges e of the tool and to wash thechips as they are cut pressure is supplied to the cutting edge of thefrom the stock backwardly through the fluted portion of the drill.

It will be noted that the thicker curved walls of the shank form a bracefor substantially more than half the sides of the flute and which brace1 extends substantially along the line of the twisttcrciie'reeietentcenstrnctien.;

Icieihifr L 1- A, tccl ci the character described ccrnbris# irggfaiubiilerelidnk. dertien Vpreyided with. 'a creleceni sheeedcendnit, dtoeren. holder d hifhebeed cntine tcci bit., eachjhayine cen-Jenineritwith .seid crescent.. shaped t) Sei tdci ebenki .teel bit he andtodi.'

blt. beierrcyided' w. a ccntindonecnter ccetr' between inecrtcrdiieicrcee. .tbiis providing e stiffer, morevv ine' ccyeiiilne. 'the bitholder eindl tool biti,

.2- in, 'n tccl, ci the eharecterdescribed e. tccl. ehenli hei/ine elcneitndinally extending chip Qleerdncefldie end e substantially centredcree-u cent shaped fluid pressure conduit, the thickness ci tbc Sidewall ci Said shnnls alone the arcuate portieri thereof, and ierSubstantially there than hel-f. the crees. sectional. circliinierelnee,being ab: lircxirnetely twiceihe thickness ci the Sidefweill et .the`central part ci Seid chipclearance nnte.

3. nv tool of the characterdesc'ribed haring a cutting bit portion enda--tnbuler shank with( e. longitudinally extending chip. clear` c@ Quitebrcyided therein, thel thicknese ci the of said shank adjacent thecentral part of said flute beine. approximately One-heli the thicknessci the cbbccifte side.- We'll ci. Seid ehenh, Seid;

Shenlr beine fcrrned with e vctrlindricdl. portieri..

the, circumferential length ciwnich.. ie ceiibetdne tielly grenierinfinite Senn-.circliniierenee- I 4.. 'A tool of the characterdescribedY hav-ing a cutting nerticfn end e. tubular cheek with e leneitndinellyertendine.- chi-p .clearanceiinte end Sibstdntielly' central.crescent shaped; fluid. bres.: eiire cciidiiit brfcrided therein Seti/dYehnnlsherel ineY e. thickened; b crticn. Side been. ne the ccn're'xside 0f said; creecentehenedccn end eriendine ebbetnntielly irfiihe'ldirecticn. di they reecticn tcJ the tcrdiie iQrceS. te., which theshanlc portion of said tool is subjeciied and bracing ghe; iii-e101"Dertien. ci the side,- cieeid finte that.; cdrrechcbdb; te the..ttineedee ci the. bit.; the tcidiie.idrceei vddid nhenkitgecl Side wallf ting rela A ioei of the. cherdcter described comprising.' n cutting.bit eerbied. abit helder portion and a 's .nk portieri. s ecnredtcgetherin abrite enshib te. icrm, n n integral structure and. having e; thinouter ceatine extending along the'outer periphery of each oisad'portions to ll the ereyiees etthepcints. ci union. 'ci Seid editionswithjeech, other end thereby ic. formV a smcctneontindodsienduninterrupted surfaceit?. A drilljoi the character described compris.-

' ine d tubularl Shank. portion, a tcclbit helder egiptrernity of saidtool bit; holder member form- Ynreylde. clearance spaces. Y K '75; Adrill, of the character described comprisfing a tuhiilar'shank portion,a tool bit', holderV rneinber and' e tc'cl bit,.member. each of Seidmembers and Said tubular Shank( beine provided yiih a' ccntinueus.longitudinally extending chip clearance, initie and each 0f Seidmembers. being provi-ded with a land extending' along the outerperiphery ci said drill adidcent to eech cuter edge.. di seid finteendei third land extending vdiene seid. cuter peribheryintermediete thenrst .20; 'daily the full diameter of the hole to be drilled meiiticnedtwo. lends., Seid lands heine` Subsidieby said drill and vtheouterperiphery of said members being relieved' between said lands tomember and e tccl bit member, each of seid members and said tubularshank being provided with af continuous. lllgitudnally ,exteilding`vchip clearance finte, one side YQnly'of said flute at the ing @heentire cutting edge of said drill and said tQQl; btmernber and tool bitholder member be- Y ing provided along the periphery of thedrill i.,adjacent the cutting edge side of said ute with i e. narrow land andseidperiphery being `provided with, a'rwide land adjacentio the otheredge of said flute andy said;` drill being provided with a third. landextending along'the. periphery ci Seid -A members. between. .saidnarrowland and seid Wide lend endthe remainder of the periphery of seidmembers, between said. lands being relieved to forni clearance., Spaces,

Y Y Y ALBERT J- NORDBERG-

